(85f) In-Situ Synthesized Nano Zero-Valent Iron-SBA-15 As Fenton Catalyst for Tetracycline Remediation from Wastewater

Nano-zero-valent Iron (nZVI), due to its high reduction ability, low cost, and non-toxicity, has been applied in various environmental remediation applications. However, the ease of agglomeration and the tendency to form a passivation layer, which reduces the effectiveness of the materials, has garnered research focus on creating a composite compound containing nZVI and a support matrix. Various support materials, such as zeolite, mesoporous silica, biochar, etc., have been reported to mitigate the severe agglomeration and oxidation of nZVI. A few studies have also reported SBA-15, an ordered mesoporous material, as support material nZVI. In these approaches, harsh chemicals (such as sodium borohydride) and high temperatures were employed to synthesize nZVI, which was then incorporated into the SBA-15 matrix. In the presented work, nZVI-SBA-15 materials were prepared through an in-situ process, where (i) green tea extract serves as a reducing agent for nZVI, and (ii) sodium metasilicate acts as a silica source, replacing the cost-intensive tetraethyl orthosilicate. Therefore, the resulting material is inexpensive and contains nZVI particles within the framework of SBA-15 rather than within its pores. The HR-TEM investigations of the synthesized nZVI-SBA-15 show the presence of nZVI particles with sizes ranging from 10 to 30 nm. The comparative N₂-sorption studies of SBA-15 and nZVI-SBA-15 reveal a minimal loss of surface area after nZVI incorporation. Additionally, ICP-MS and XPS analyses (narrow Fe 2p scan) were conducted to determine the iron content and state in the synthesized material. Mössbauer spectroscopic analysis will be carried out to determine the oxidation state of iron. Tetracycline (TC) degradation with the presence of H₂O₂ was carried out to evaluate the catalytic performance of the material. For comparison, the performance of in-situ iron/Fe-SBA-15 and ex-situ nZVI/SBA-15 was also determined. The performance data reveal that the in-situ nZVI-SBA-15 has 1.8 times, and 2.3 times better TC degradation compared to in-situ iron/SBA-15 and ex-situ nZVI/SBA-15 powders, respectively. The TC degradation in real wastewater, achieved by spiking wastewater with TC, was performed to simulate the practical applicability of the catalyst.